Re: [PATCH v6 2/2] tpm: add securityfs support for TPM 2.0 firmware event log
From: Jarkko Sakkinen
Date: Sat Nov 26 2016 - 10:48:13 EST
On Sat, Nov 26, 2016 at 07:45:39AM -0500, Nayna Jain wrote:
> Unlike the device driver support for TPM 1.2, the TPM 2.0 does
> not support the securityfs pseudo files for displaying the
> firmware event log.
>
> This patch enables support for providing the TPM 2.0 event log in
> binary form. TPM 2.0 event log supports a crypto agile format that
> records multiple digests, which is different from TPM 1.2. This
> patch enables the tpm_bios_log_setup for TPM 2.0 and adds the
> event log parser which understand the TPM 2.0 crypto agile format.
>
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
I would not rush with new patch set versions as long as the testing is
almost completely lacking. I didn't even have time to read the previous
version properly before this came out.
> ---
> drivers/char/tpm/Makefile | 2 +-
> .../char/tpm/{tpm_eventlog.c => tpm1_eventlog.c} | 35 ++--
> drivers/char/tpm/tpm2_eventlog.c | 214 +++++++++++++++++++++
> drivers/char/tpm/tpm_eventlog.h | 70 +++++++
> 4 files changed, 306 insertions(+), 15 deletions(-)
> rename drivers/char/tpm/{tpm_eventlog.c => tpm1_eventlog.c} (95%)
> create mode 100644 drivers/char/tpm/tpm2_eventlog.c
>
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index a05b1eb..3d386a8 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -3,7 +3,7 @@
> #
> obj-$(CONFIG_TCG_TPM) += tpm.o
> tpm-y := tpm-interface.o tpm-dev.o tpm-sysfs.o tpm-chip.o tpm2-cmd.o \
> - tpm_eventlog.o
> + tpm1_eventlog.o tpm2_eventlog.o
> tpm-$(CONFIG_ACPI) += tpm_ppi.o tpm_acpi.o
> tpm-$(CONFIG_OF) += tpm_of.o
> obj-$(CONFIG_TCG_TIS_CORE) += tpm_tis_core.o
> diff --git a/drivers/char/tpm/tpm_eventlog.c b/drivers/char/tpm/tpm1_eventlog.c
> similarity index 95%
> rename from drivers/char/tpm/tpm_eventlog.c
> rename to drivers/char/tpm/tpm1_eventlog.c
> index fe7e3fa..e9a092b 100644
> --- a/drivers/char/tpm/tpm_eventlog.c
> +++ b/drivers/char/tpm/tpm1_eventlog.c
> @@ -390,9 +390,6 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
> unsigned int cnt;
> int rc;
>
> - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> - return 0;
> -
> rc = tpm_read_log(chip);
> if (rc)
> return rc;
> @@ -407,7 +404,13 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
> cnt++;
>
> chip->bin_log_seqops.chip = chip;
> - chip->bin_log_seqops.seqops = &tpm_binary_b_measurements_seqops;
> + if (chip->flags & TPM_CHIP_FLAG_TPM2)
> + chip->bin_log_seqops.seqops =
> + &tpm2_binary_b_measurements_seqops;
> + else
> + chip->bin_log_seqops.seqops =
> + &tpm_binary_b_measurements_seqops;
> +
>
> chip->bios_dir[cnt] =
> securityfs_create_file("binary_bios_measurements",
> @@ -418,17 +421,21 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
> goto err;
> cnt++;
>
> - chip->ascii_log_seqops.chip = chip;
> - chip->ascii_log_seqops.seqops = &tpm_ascii_b_measurements_seqops;
> + if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
>
> - chip->bios_dir[cnt] =
> - securityfs_create_file("ascii_bios_measurements",
> - 0440, chip->bios_dir[0],
> - (void *)&chip->ascii_log_seqops,
> - &tpm_bios_measurements_ops);
> - if (IS_ERR(chip->bios_dir[cnt]))
> - goto err;
> - cnt++;
> + chip->ascii_log_seqops.chip = chip;
> + chip->ascii_log_seqops.seqops =
> + &tpm_ascii_b_measurements_seqops;
> +
> + chip->bios_dir[cnt] =
> + securityfs_create_file("ascii_bios_measurements",
> + 0440, chip->bios_dir[0],
> + (void *)&chip->ascii_log_seqops,
> + &tpm_bios_measurements_ops);
> + if (IS_ERR(chip->bios_dir[cnt]))
> + goto err;
> + cnt++;
> + }
>
> return 0;
>
> diff --git a/drivers/char/tpm/tpm2_eventlog.c b/drivers/char/tpm/tpm2_eventlog.c
> new file mode 100644
> index 0000000..cf9fea0
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2_eventlog.c
> @@ -0,0 +1,214 @@
> +/*
> + * Copyright (C) 2016 IBM Corporation
> + *
> + * Authors:
> + * Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
> + *
> + * Access to TPM 2.0 event log as written by Firmware.
> + * It assumes that writer of event log has followed TCG Spec 2.0
> + * and written the event struct data in little endian. With that,
> + * it doesn't need any endian conversion for structure content.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/seq_file.h>
> +#include <linux/fs.h>
> +#include <linux/security.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +#include "tpm.h"
> +#include "tpm_eventlog.h"
> +
> +static int calc_tpm2_event_size(struct tcg_pcr_event2 *event,
> + struct tcg_pcr_event *event_header)
> +{
> + struct tcg_efi_specid_event *efispecid;
> + struct tcg_event_field *event_field;
> + void *marker, *marker_start;
Split to two lines.
> + int i, j;
Split to two lines.
> + u16 halg;
> + u32 halg_size;
> + size_t size = 0;
Please do not initialize variables unless you need to initialize them in
the declaration. It is not a good practice. And in here it is especially
misleading because you don't initialize anything else. I assumed first
that there might be a special reason why size is initialized.
> +
> + /*
> + * NOTE: TPM 2.0 supports extend to multiple PCR Banks. This implies
> + * event log also has multiple digest values, one for each PCR Bank.
> + * This is called Crypto Agile Log Entry Format.
> + * TCG EFI Protocol Specification defines the procedure to parse
> + * the event log. Below code implements this procedure to parse
> + * correctly the Crypto agile log entry format.
> + * Example of Crypto Agile Log Digests Format :
> + * digest_values.count = 2;
> + * digest_values.digest[0].alg_id = sha1;
> + * digest_values.digest[0].digest.sha1 = {20 bytes raw data};
> + * digest_values.digest[1].alg_id = sha256;
> + * digest_values.digest[1].digest.sha256 = {32 bytes raw data};
> + * Offset of eventsize is sizeof(count) + sizeof(alg_id) + 20
> + * + sizeof(alg_id) + 32;
> + *
The bellow code does not implement anything. I woud just keep the first
paragraph in this comment.
> + * Since, offset of event_size can vary based on digests count, offset
> + * has to be calculated at run time. void *marker is used to traverse
> + * the dynamic structure and calculate the offset of event_size.
> + */
> +
> + marker = event;
> + marker_start = marker;
> + marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
> + + sizeof(event->digests.count);
> +
> + efispecid = (struct tcg_efi_specid_event *) event_header->event;
> +
> + for (i = 0; (i < event->digests.count) && (i < HASH_COUNT); i++) {
> + halg_size = sizeof(event->digests.digests[i].alg_id);
> + memcpy(&halg, marker, halg_size);
> + marker = marker + halg_size;
> + for (j = 0; (j < efispecid->num_algs); j++) {
> + if (halg == efispecid->digest_sizes[j].alg_id) {
> + marker = marker +
> + efispecid->digest_sizes[j].digest_size;
> + break;
> + }
> + }
> + }
> +
> + event_field = (struct tcg_event_field *) marker;
> + marker = marker + sizeof(event_field->event_size)
> + + event_field->event_size;
> + size = marker - marker_start;
> +
> + if ((event->event_type == 0) && (event_field->event_size == 0))
> + return 0;
> +
> + return size;
> +}
> +
> +static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
> +{
> + struct tpm_chip *chip = m->private;
> + struct tpm_bios_log *log = &chip->log;
> + void *addr = log->bios_event_log;
> + void *limit = log->bios_event_log_end;
> + struct tcg_pcr_event *event_header;
> + struct tcg_pcr_event2 *event;
> + int i;
> + size_t size = 0;
Again.
> +
> + event_header = addr;
> +
> + size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event)
> + + event_header->event_size;
> +
> +
Why two newline characters?
> + if (*pos == 0) {
> + if (addr + size < limit) {
> + if ((event_header->event_type == 0) &&
> + (event_header->event_size == 0))
> + return NULL;
> + return SEQ_START_TOKEN;
> + }
> + }
> +
> + if (*pos > 0) {
> + addr += size;
> + event = addr;
> + size = calc_tpm2_event_size(event, event_header);
> + if ((addr + size >= limit) || (size == 0))
> + return NULL;
> + }
> +
> + /* read over *pos measurements */
What does this comment tell that the code below does not tell? And in
addition to that it is incorrect. You are reading over *pos - 1
measurements, not *pos measurements.
> + for (i = 0; i < (*pos - 1); i++) {
> + event = addr;
> + size = calc_tpm2_event_size(event, event_header);
> +
> + if ((addr + size >= limit) || (size == 0))
> + return NULL;
> + addr += size;
> + }
> +
> + return addr;
> +}
> +
> +static void *tpm2_bios_measurements_next(struct seq_file *m, void *v,
> + loff_t *pos)
> +{
> + struct tcg_pcr_event *event_header;
> + struct tcg_pcr_event2 *event;
> + struct tpm_chip *chip = m->private;
> + struct tpm_bios_log *log = &chip->log;
> + void *limit = log->bios_event_log_end;
> + void *marker;
> + size_t event_size = 0;
Again.
> +
> + event_header = log->bios_event_log;
> +
> + if (v == SEQ_START_TOKEN) {
> + event_size = sizeof(struct tcg_pcr_event)
> + - sizeof(event_header->event)
> + + event_header->event_size;
> + marker = event_header;
> + } else {
> + event = v;
> + event_size = calc_tpm2_event_size(event, event_header);
> + if (event_size == 0)
> + return NULL;
> + marker = event;
> + }
> +
> + marker = marker + event_size;
> + if (marker >= limit)
> + return NULL;
> + v = marker;
> + event = v;
> +
> + event_size = calc_tpm2_event_size(event, event_header);
> + if (((v + event_size) >= limit) || (event_size == 0))
> + return NULL;
> +
> + (*pos)++;
> + return v;
> +}
> +
> +static void tpm2_bios_measurements_stop(struct seq_file *m, void *v)
> +{
> +}
> +
> +static int tpm2_binary_bios_measurements_show(struct seq_file *m, void *v)
> +{
> + struct tpm_chip *chip = m->private;
> + struct tpm_bios_log *log = &chip->log;
> + struct tcg_pcr_event *event_header = log->bios_event_log;
> + struct tcg_pcr_event2 *event = v;
> + void *temp_ptr;
> + size_t size = 0;
> +
> + if (v == SEQ_START_TOKEN) {
> + size = sizeof(struct tcg_pcr_event)
> + - sizeof(event_header->event)
> + + event_header->event_size;
> +
> + temp_ptr = event_header;
> +
> + if (size > 0)
> + seq_write(m, temp_ptr, size);
> + } else {
> + size = calc_tpm2_event_size(event, event_header);
> + temp_ptr = event;
> + if (size > 0)
> + seq_write(m, temp_ptr, size);
> + }
> +
> + return 0;
> +}
> +
> +const struct seq_operations tpm2_binary_b_measurements_seqops = {
> + .start = tpm2_bios_measurements_start,
> + .next = tpm2_bios_measurements_next,
> + .stop = tpm2_bios_measurements_stop,
> + .show = tpm2_binary_bios_measurements_show,
> +};
> diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
> index 1660d74..7e33b90 100644
> --- a/drivers/char/tpm/tpm_eventlog.h
> +++ b/drivers/char/tpm/tpm_eventlog.h
> @@ -5,6 +5,9 @@
> #define TCG_EVENT_NAME_LEN_MAX 255
> #define MAX_TEXT_EVENT 1000 /* Max event string length */
> #define ACPI_TCPA_SIG "TCPA" /* 0x41504354 /'TCPA' */
> +#define HASH_COUNT 3
> +#define MAX_TPM_LOG_MSG 128
> +#define MAX_DIGEST_SIZE 64
Where have been the values for these constants derived? You should
anyway prefix them with TPM_.
> #ifdef CONFIG_PPC64
> #define do_endian_conversion(x) be32_to_cpu(x)
> @@ -73,6 +76,73 @@ enum tcpa_pc_event_ids {
> HOST_TABLE_OF_DEVICES,
> };
>
> +/*
> + * All the structures related to TPM 2.0 Event Log are taken from TCG EFIi
> + * Protocol * Specification, Family "2.0". Document is available on link
> + * http://www.trustedcomputinggroup.org/tcg-efi-protocol-specification/
> + * Information is also available on TCG PC Client Platform Firmware Profile
> + * Specification, Family "2.0"
> + * Detailed digest structures for TPM 2.0 are defined in document
> + * Trusted Platform Module Library Part 2: Structures, Family "2.0".
> + */
> +
> +/* TPM 2.0 Event log header algorithm spec. */
> +struct tcg_efi_specid_event_algs {
> + u16 alg_id;
> + u16 digest_size;
> +} __packed;
> +
> +/* TPM 2.0 Event log header data. */
> +struct tcg_efi_specid_event {
> + u8 signature[16];
> + u32 platform_class;
> + u8 spec_version_minor;
> + u8 spec_version_major;
> + u8 spec_errata;
> + u8 uintnsize;
> + u32 num_algs;
> + struct tcg_efi_specid_event_algs digest_sizes[HASH_COUNT];
> + u8 vendor_info_size;
> + u8 vendor_info[0];
> +} __packed;
> +
> +/* TPM 2.0 Event Log Header. */
> +struct tcg_pcr_event {
> + u32 pcr_idx;
> + u32 event_type;
> + u8 digest[20];
> + u32 event_size;
> + u8 event[MAX_TPM_LOG_MSG];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile algorithm and respective digest. */
> +struct tpmt_ha {
> + u16 alg_id;
> + u8 digest[MAX_DIGEST_SIZE];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile digests list. */
> +struct tpml_digest_values {
> + u32 count;
> + struct tpmt_ha digests[HASH_COUNT];
> +} __packed;
> +
> +/* TPM 2.0 Event field structure. */
> +struct tcg_event_field {
> + u32 event_size;
> + u8 event[MAX_TPM_LOG_MSG];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile log entry format. */
> +struct tcg_pcr_event2 {
> + u32 pcr_idx;
> + u32 event_type;
> + struct tpml_digest_values digests;
> + struct tcg_event_field event;
> +} __packed;
Your alignment is broken. You sometimes align and sometimes do not.
For struct fields it does not make sense align fields at all since it
does not "scale". It is done in some places in the driver but for new
code it is absolutely disallowed. Thus, the right way to fix this is to
remove all the aligment.
For enums it does make sense and improves readability.
> +
> +extern const struct seq_operations tpm2_binary_b_measurements_seqops;
> +
> #if defined(CONFIG_ACPI)
> int tpm_read_log_acpi(struct tpm_chip *chip);
> #else
> --
> 2.5.0
/Jarkko